How accurate is Scottrade streaming quotes?

I'm looking at it change numbers every seconds but when I go to something like marketwatch where it also change every second, I'm getting a different value. Which one is more accurate? Where can I get the most accurate information as far as the current price of the stock? Thanks.

i have scottrade and it works for me. except for that one time when it had to "establish" and i didnt realize it so i bought a stock more than what i should have. but yea, overall scottrade is up to the sec.